


The Curse of the Black Diamond

by Tsubasa Kurono (kurotsuba)



Series: A Snitch in Time: A Harry Potter & Fantastic Beasts Fanfiction Archive [7]
Category: Fantastic Beasts and Where to Find Them (Movies), Harry Potter - J. K. Rowling, Sherlock (TV), Sherlock Holmes & Related Fandoms
Genre: 221B Baker Street, Banter, British Museum, Case Fic, Challenge Response, Contest Entry, Crimes & Criminals, Cross-Posted on FanFiction.Net, Cross-Posted on Wattpad, Crossover, Curses, Detectives, Epistolary, Experimental Style, Gen, Harry Potter Next Generation, Humor, Jewelry, John Watson's Blog, London, Magic, Magic Revealed, Muggle London, Muggle/Wizard Relations, Murder Mystery, Mystery, Nifflers, Originally Posted on FanFiction.Net, POV First Person, POV John Watson, Parody, Post-Finale, Sarcasm, Thriller, black diamond
Language: English
Status: In-Progress
Published: 2019-05-29
Updated: 2019-07-30
Packaged: 2020-03-08 17:37:43
Rating: Teen And Up Audiences
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 3
Words: 2,406
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/18899437
Author URL: https://archiveofourown.org/users/kurotsuba/pseuds/Tsubasa%20Kurono
Summary: "When logic meets magic, Sherlock sets out on his most intriguing case yet."A strange client with an even stranger creature on the loose find their way to 221B Baker Street, coming face to face with John Watson and his eccentric roommate, Sherlock Holmes. With the London Jewelry Roadshow just a few days away, it's up to the quartet to stop the deadly curse of the Black Diamond before the biggest gemstone event of the year turns into an absolute nightmare for both the wizarding world and the Muggle world.Ongoing.Originally posted onFanFiction.Net;Reprints available onWattpadandHPFF.





	1. Cover Page

**Author's Note:**

> " _It is the dim haze of mystery that adds enchantment to pursuit._ "  
> —Antoine Rivarol

**Notes for the Chapter:**

> Cover design © Tsubasa Kurono;  
> Diamond stock image from Pexels.


	2. Preface

**Summary for the Chapter:**

> " _It is the dim haze of mystery that adds enchantment to pursuit._ "  
> —Antoine Rivarol

As the quote says, when Rowling's Wizarding World collides with the endearing characters of Doyle's Sherlock Holmes series… When both mystery and magic come together and bring about an unstoppable thrill to pursuit the unknown…

Oh yes, I know you're already itching to dive right into the story. Go ahead and skip to the next chapter if you must, but for those who can hold your horses a bit longer, let me say a few words beforehand.

Firstly, a really big thank you for checking out my work. It means a lot to me, and it is the first step to build a connection between you, the awesome readers, and me, a budding writer with nothing (yet) but dreams waiting to be turned into stories like this. Secondly, I must confess that English is not my native language, and I'm still learning to improve, to get better at it. What's better than writing and sharing my works to the world to show my passion for the language—and of course, for the fandoms that have inspired me with amazing ideas that I know I must pen them down, turning my dreams into reality?

This story originally started as a competition piece hosted on a FanFiction.Net forum, but after binging the TV series in two weeks, I felt the need to make this idea more than just a single-chapter attempt. I have been mostly writing oneshots and short stories (at times poetry) for quite a while; it's about time I return and write a multi-chapter novel.

I do try my best to stay true to Rowling's Wizarding World, Doyle's original Sherlock Holmes style, and sticking as much as I can to the canon in the Sherlock TV series. That's a lot of things to take note and watch out for at once, and I am reminded again how challenging it is to write crossover stories. However, I may take some liberties to diverge from the canon for the sake of maintaining logic within this story, independent from the respective fandoms. I hope you can enjoy the adventure of John and Sherlock stepping into the magical realm brought by an unlikely person from among Rowling's next generation characters as much as I do while writing this work.

Thank you for reading an author's rambling, and I shan't hold you back any longer. Let's dive into the story proper and have fun!

—Tsubasa Kurono


	3. The Gold Sniffler

Having known Sherlock Holmes and his eccentricity for over a year, I was led to believe that nothing in this world could astound me more than him delivering a cutting-edge deduction that sounded like a semi-automatic machine gun emptying its bullets happily at the culprits behind every heinous crime. I had always felt amazed, fascinated, even intimidated by his sharp observational skills that made me feel like he could read minds. Not to mention his keen but sophisticated intellect that snorted at the idea of morality and ethics, citing them as "useless facts elbowing out the useful ones, thus reducing the brain's already limited capacity to learn the more important things in my field of work," in his words. Sherlock solved mysteries not in the name of justice, but merely as a stimulant to keep his shrewd mind occupied—he had a great love for the gore and death that accompanied the process of piecing the ugly jigsaw together. It was my own moral compass and the trauma from my service in the War in Afghanistan that kept me from getting swept away by Sherlock's dangerous charm, to share his questionable view about murder as a form of entertainment. That being said, of all the cases I had the pleasure to participate in, none of them stood out like this singularity, so bizarre that even Sherlock was forced to re-evaluate his belief system; it was a case that involved something we never wanted to believe was real.

The event occurred a few days before the London Jewellry Roadshow held at the World Conservation and Exhibition Centre in the British Museum. I could still vividly recall how the morning started on that fateful day; I found Sherlock standing in the living room with an expression I had seen only once, a month ago, during the showdown with his sister, Eurus Holmes. Then I glanced around the lounge in horror.

"What in the devil happened in here?"

"That's what I'd like to know, too," he said as he kicked the fallen books and cushions aside, the dark look still stuck on his face. "I don't think we have anything valuable to lose in this house, but clearly, whoever this fellow is, they have a peculiar liking for all things shiny."

"Something shiny? Like money?"

"Not just money; besides, paper notes are worth more and they're obviously not shiny." Sherlock continued to rummage through the mess, darting to and fro between the living and dining rooms, which was making me a little dizzy. "Coins, yes, and anything metallic or something that can give off an expensive glint." He finally stopped short before my unfocused eyes with a wry smile. "Even an iPhone with stainless steel casing."

"What?"

"Ingenious, isn't it?" he breathed, flopping his tall frame into an armchair after he had knocked off the stack of papers from the seat. "Our thief was thorough enough to smash your laptop and remove the gold nuggets from your motherboard."

My wide eyes followed Sherlock's finger to the remnants of the computer where I used to keep these case notes and write blog entries about them. It had been reduced to a pile of black plastic bits, and I was glad I had saved all the important data in cloud storage. Else, I'd have felt too devastated to face the client who had thundered up the stairs to the living room.

Although I admit that fashion had never been my strong suit, not even against Sherlock who could make ladies swoon with a long coat over his straight-cut clothes, the newcomer had swept the rug out from under my feet the moment he burst into the lounge, clearly breathless from the effort of climbing the narrow staircase to reach our quarters. The man appeared to be in his mid-thirties: lean and tall with a tan complexion, complete with a mop of curly copper-brown hair that added a humourous twinkle in his blue eyes. The most notable feature about him, however, was the most bizarre set of clothes I had ever seen in my life. I knew my history well enough that the gentleman looked like someone who had popped out of the Edwardian era the moment he removed the billowing travelling cloak from his shoulders, revealing a three-piece pinstripe suit that clashed horribly with his hair. The polka-dot necktie did not help, either—I couldn't think of anything that would go well with such a violent shade of purple, and it was certainly not whatever the stranger was wearing now. The wooden stick he held out before him was the finishing touch to his comical appearance, and it was my curious stare at his defensive stance that the man hastily put the twig away in his blazer.

"Sorry for the rude greeting," he said, smoothing out his suit with a hand before smiling at us nervously. "My name is Rolf Scamander, and I apologise for the mess my Niffler has caused." He gestured around the living room with a shaky hand, his eyes moving from me to Sherlock.

"Niffler?"

"My, uh, pet," Rolf supplied; he seemed less skittish as he began to move around the lounge, poking his head into our dining room with raised eyebrows. "Ran off the moment I returned from my Ilvermorny trip. America," he added when he noticed our questioning looks at him.

Sherlock, who had been quiet throughout my exchange with our oddly dressed client, finally sprang to his feet and studied Rolf closely, the same way he would examine a corpse for clues. "Curious," he said, cupping a hand under his chin and flipping around the gentleman's clothes with the other. "Yes, I do smell the stink unique to the badly sanitised interior of an aircraft, but it's strange that this stench still stays on your clothes given that the airport is kilometres away from here. There are no other indications of how you've been travelling around except on foot." He gestured at the cuffs around Rolf's fitting pants. "Mud splash, but from the mark it looks like you plopped into the puddle from higher ground rather than just walking into one, but no sign on your otherwise clean and well-ironed clothes to suggest that you'd jumped into mud by climbing over obstacles or hopping down a fire escape. And the things you've been saying... I'm intrigued. They don't sound remotely familiar, not even with all the useless world facts John—my partner there—has fed me with over the year."

"Sherlock," I cleared my throat and tapped a finger on my roommate's shoulder. "You're scaring our client." My eyes travelled from Sherlock's irritated face to Rolf's look of petrified awe.

"Scaring him? I think not," Sherlock huffed, but at least he stepped back to give the poor guy some breathing space. "His facial muscles are contorted into what seems to be fear, but his pupils are not dilated; appears normal, suggesting that he's still in control, that he's more amused than frightened. Very different from how most people have reacted to my deductions upon our first encounter so far. Including you, John." At which point I rolled my eyes at my friend.

"'Deductions,' as you call this, sir?" Rolf echoed, stepping forward and moving closer to Sherlock. The shorter man with funny clothes seemed to be reading my partner, in a way that seemed as if he could stare right into Sherlock's figuratively oversized head that often gave off both an air of intimidating perspicacity and arrogant ignorance for anything that didn't tickle his interest.

"Well, 'observations,' then, if you're so particular about my word choice," Sherlock shrugged and broke the eye contact, helping himself to the tea that Mrs. Hudson, our landlady, had so kindly prepared for us before she left the house. "So, what's your case?"

"Case?" The amused look seemed to be permanently stuck on Rolf's face as he watched Sherlock sweeping off the tax invoices on his armchair before sitting down. "I'm here to look for my Niffler. I know it's still hiding in this house."

"Hiding? In our house? What—"

Before I could complete my sentence, we were startled by a loud crash coming from the end of the hallway—Sherlock's room. My friend's face darkened as he dashed out of the lounge before either Rolf or I could react.

"No, no, no... NO, DON'T TOUCH THAT!" The sound of Sherlock's furious screams mixed with the din of breaking glass from behind the closed door was so terrible that any sane person wouldn't want to go near at all. With the exception of our oddball client, who calmly pulled out the wooden stick from the inner pocket of his pinstripe jacket and held it before him.

"Sir!" Rolf shouted, rushing up to Sherlock's door. He grasped the knob and shook it, with a look of annoyance that broke the impassive mask on his face when it was found to be locked. "Don't hurt it! Let me in! _Alohomora!_ "

We jumped away from the door the moment it burst open; I thought I saw a small black creature somersaulting out of the room before my eyes focused on a hysterical Sherlock who flew past me in a whirlwind of blue (he was wearing a midnight-blue bathing robe). Rolf caught the furry little tyke with an outstretched hand, out of the reach of Sherlock's attempt to claw it down.

"Easy there," Rolf cooed as the three of us returned to the living room, breathless and sweaty from all the action just to catch up with the creature in our client's arms. It was small, black, with beady eyes and a pink snout.

"A baby... platypus?" I tried to joke, but Sherlock had to be a killjoy and dismissed my feeble attempt to lighten the tension in the room with brutal sarcasm.

"How can that be a platypus? It doesn't look remotely like one at all. Platypuses have wider, darker snouts, not pink; they have brown, not black fur. Also, they have webbing on their feet, but this one has claws, clearly meant for digging dirt and not swimming in a pool. I'd say it's more like a lawn mole."

"I was only kidding, Sherlock," I snapped. "Show-off."

"This is a Niffler," Rolf explained; I swore he was trying hard not to laugh at us. "And you're right; it doesn't swim, but it's a good digger. Nifflers are great at finding treasures because of their predilection for anything that glitters." With a sigh, he turned the creature upside down and shook it. From the pouch before its middle, various objects fell onto the ground with a series of clings and thuds: coins, paper clips, knives and forks... including Sherlock's stainless steel-cased iPhone, and the gold bits taken out of my laptop's motherboard. "Really sorry about all these things my buddy—Nicky—has taken from your house. You can have them back now."

"Well," Sherlock arched an eyebrow at the pile of shiny items on the carpeted floor. "Your little friend has an interesting taste for metallic junk as much as real gold."

"Nicky is unique from other Nifflers—while it's terrible at discerning between real and fake rare metals, it's never wrong between real and fake gemstones."

"Gemstones?" Sherlock sat up straighter and leaned forward, finally showing Rolf genuine interest for the first time this morning. "For the London Jewellry Roadshow in three days time, yes? Now that is _intriguing_." The corner of his lips curled up into a smile.

"I'm Sherlock Holmes, and do pull a chair and sit down. Tell me your story."

"John Watson," I added, sinking into my armchair that had its back facing the dining room, looking at Rolf expectantly.

The stranger's tale, however, was beyond what Sherlock and I could ever imagine. It was a world that delved into things that my best friend often dismissed as dumb superstitions and wild fantasies, only to finally acknowledge that magic was indeed as real as all the essential facts he could memorise from the _Encyclopædia Britannica_.

**Author's Note:**

> Prompt:  
> THC | [Y4R8] Crossover | [Fandom] Sherlock (TV series)
> 
> Fanfiction by Tsubasa Kurono.  
>  _Sherlock_ (TV series) created by Steven Moffat and Mark Gatiss,  
> Based on the _Sherlock Holmes_ series by Arthur Conan Doyle;  
>  _Wizarding World_ © J. K. Rowling, Warner Bros.
> 
> Inspiration:  
> "[The Houses Competition](https://www.fanfiction.net/forum/The-Houses-Competition/202668)" by MoonlightForgotten.


End file.
